Full complement roller bearings 10, such as the one shown in FIG. 1, are typically made by first draw forming an annular metal sleeve from strip stock to create an outer cup 12. Typically, both ends of the sleeve are formed to provide an integral roller retaining feature that prevents both axial and radial displacement of the corresponding plurality of rollers 18. First, an integral, radially inwardly extending flange 14 with an axially extending lip 16 is formed at a first end of the annular sleeve, commonly referred to as the “bottom” of the outer cup. Next, rollers 18 which have axial projections 22, commonly called trunnions, at each end are placed in the annular sleeve. The trunnions of the rollers can range in shape from complex (as shown in FIG. 1) to simple conical. The first end of each trunnion roller 18 is disposed between an outer raceway formed by the sleeve and the corresponding axially extending lip 16 so that the first end of each trunnion roller 18 is held in place radially in the cupped end.
Lastly, an integral, radially inwardly extending curled flange 15 is formed at the opposite end of the annular sleeve so that axial projections 22 on the second end of trunnion rollers 18 are disposed between the outer raceway and a corresponding axially extending lip 17 on the inner perimeter of flange 15. As such, both ends of each trunnion roller 18 are radially and axially retained.
Flanges 14 and 15 and their corresponding lips 16 and 17, respectively, of the outer cup form axial thrust faces for the ends of the plurality of trunnion rollers 18. With a full complement of rollers, the surfaces where the ends of the trunnion rollers contact the flanges must be hardened to protect them from wear. Typically, the annular sleeve from which outer cup 12 is produced is made of low carbon steel and must be heat treated to harden it and, thereby, provide the outer raceway. However, once the annular sleeve is carburized through heating, flange 15 cannot be easily curled without cracking.
One approach for making the formed lips 16 and 17 at the ends of the corresponding flanges 14 and 15, respectively, requires assembling the components of the roller bearing into outer cup 12 prior to it being heat treated. With the components fully assembled, second flange 15 and lip 17 can be formed prior to hardening outer cup 12, thereby preventing cracking. Thereafter, the entire roller bearing 10 is heat treated. This process dictates that the materials used for rollers 18 must be amenable to heat treatment. Where differing materials are used for outer cup 12 and rollers 18, it is common to subject rollers 18 to a heat treatment prior to the heat treatment of the assembled bearing, adding to cost. As well, the presence of rollers 18 in outer cup 12 during heat treatment can block portions of the cup, which are in contact with the rollers, resulting in “soft” spots and reduced cup life. As well, the presence of rollers in outer cup 12 during heat treatment can lead to increased carbon deposits, requiring cleaning of the bearing.
Alternately, it is known to form flanges 14 and 15, with lips 16 and 17, prior to insertion of rollers 18. Outer cup 12 is then heat treated, followed by the insertion of rollers 18. Assembly of rollers 18 into the heat treated outer cup 12 is a complicated and somewhat costly process. In yet another process, it is known to use a copper mask to prevent hardening of the portion of outer cup 12 that is to be top flange 15. After heat transferring outer cup 12, the copper mask is removed with a chemical solution so that top flange 15 can be formed. This process is costly and can have adverse and environmental impact.
One solution, as shown in FIG. 2, has been to produce a roller bearing assembly 30 including a cage 36 which defines a roller pocket 38 for each roller 40. The cage eliminates the need to provide an axially extending lip on the inner perimeter of the flanges 34 of the bearing's outer cup 32. However, as cage 36 includes axially extending members 38 disposed between adjacent rollers 40, the number of rollers as compared to the full complement bearing assembly 10 must be reduced, meaning the loading that bearing assembly 30 can withstand is less than that of bearing assembly 10.
The present invention recognizes and addresses considerations of prior art constructions and methods.